A guy bought my MacKissic that went on my Gravely to shred his raspberry canes because his DR
chipper-only wouldn't do them well. Strangely, that MacKissic, very much like the TPH-122 one I have now for the PTO on the JD, didn't have a
chipper blade.
I mainly use the shredder part of my TPH-122 except for bigger, mostly limb stuff. I, like the other poster, probably use the
chipper about 30% of the time and the shredder 70%. Of course, for doing leaves, they're 100% shredding. Best thing for leaves is one of those vacuum-them-up shredders. A friend of mine has one of those. However, the TPH-122 (and was identical on the Gravely-mount MacKissic I had) has a 2 part hopper that'll open wide to make dribbling things like leaves into it.
A fellow master gardener has a
chipper only machine. He said the cost of getting the
chipper blades reground is quite expensive on it. On my TPH-122, it was $5. A new (single) blade for it is $57. I just swapped the new blade, which is in need of a regrind now, for the reground blade. It's a very easy operation. Think the process of changing out the blades on a
chipper only machine would be more like the process of changing out or rotating the hammers on a shredder: a little bit more involved. Hammers on my MacKissic seem to be hardly wearing; whereas, the
chipper blade doesn't last that long before needing regrinding. Bet it's not much longer for the blades on a
chipper only machine.
Ralph